The invention generally relates to an intramedullary nail. Particularly, the invention relates to an intramedullary nail and a locking member, wherein the intramedullary nail comprises a locking hole arrangement for angularly stable receipt of the locking member. The locking member may be, for example, a cross-locking bone screw. A method of implanting such a nail is also disclosed.
In general, an intramedullary nail may be for example a femur nail, a humeral nail or a tibia nail. Usually, the leading end portion which may at first be introduced into a medullary channel of a bone and which may also be denoted as non-driving end portion of the intramedullary nail, comprises two or more through holes adapted to receive locking screws.
At present inserting locking screws in holes formed in the leading end of implanted intramedullary nails is problematic, namely because of the amount of radiation required during the determination of the position and orientation of transverse locking holes. Furthermore, it is time consuming and ideally requires well-trained and experienced personal. Therefore, it has a significant influence of the overall operation room time required.
Currently, locking of the non-driving end portion of an intramedullary nail is performed mostly freehand, by inserting a first locking screw into and through a first through hole. Due to the fact that the insertion is performed more or less blindly, the screw will in most cases not exactly hit the through hole so that the nail will be slightly displaced or even deformed to accommodate the locking screw extending through the through hole. However, this first screw will be able to move relative to the nail when forces are applied on the nail and screw.
For a locking providing angular stability, a second screw may be inserted through a second through hole adjacent the first hole. Also the second screw will in most cases not exactly hit the second through hole. Accordingly, the second screw has to be urged through the hole, with the result that the combination of the first and second screws will provide an angle-stable fixation of the intramedullary nail, i.e. a fixation with no movement of a screw relative to the nail.
However, such a fixation of an intramedullary nail requires the insertion of two screws, wherein each insertion of a screw through the leading end portion of an intramedullary nail is difficult and thus time consuming.
According to U.S. Pat. No. 7,247,157, a deformable ring may be arranged between a threaded bore and the thread of a bone screw to achieve an angle-stable locking. U.S. Patent Application Publication No. 2006/0095040 proposes a deformable sleeve on a locking screw, for introducing the screw backlash-free into a transverse hole of a marrow nail. Alternatively, U.S. Patent Application Publication No. 2006/0064095 proposes a passage extending through a screw head and an external thread generally parallel the longitudinal axis of the screw for accommodating a longitudinal wedge element. As a result, any gap between the locking screw and an intramedullary nail is eliminated and the screw is wedged in position in a transverse hole of the intramedullary nail.